Weathering modeling can introduce blemishes such as dirt, rust, cracks and scratches to virtual scenery. It is an important visual cue in photorealism as weathering effects appear everywhere in our daily life. Traditionally, blemishes are generated by combining many hand-painted textures. Such a process is labor intensive, especially if a weathering sequence has to be painted by hand and the consistency between consecutive frames is maintained manually. While some physically-based techniques can automatically simulate a number of aging effects, a drawback exists in that a new model has to be developed for each specific effect in conjunction with a detailed understanding of the underlying physical process. In addition, sometimes a physically-based simulation is not possible because the aging process (physical, chemical, biological, and combinations thereof) is not fully understood or too complex to simulate. Thus, a need exists for better techniques to simulate weathering or aging. Various exemplary techniques disclosed herein aim to satisfy this need or other needs.